Ditching machines for submarine cable

ABSTRACT

A ditching machine for digging a ditch for submarine cable comprising a main body having stabilizing means which is divided into front and rear parts and jointed so as to be bendable only up and down, and a cutting bit mounted rigidly under said rear part of the main body, to prevent the entering of the head of said stabilizing means into earth and sand on the sea-bottom and to provide stable cable burying without regard to whether the layer at sea-bottom is hard or soft.

United States Patent [191 Ezoe et al.

[ Aug. 12, 1975 1 DITCHING MACHINES FOR SUBMARINE CABLE [75] lnventors: Takuji Ezoe; Kikuo Shirai, both of Tokyo, Japan [73] Assignee: Kokusai Cable Ship Co., Ltd.,

Tokyo, Japan [22] Filed: June 7, 1973 [21] Appl. No.: 367,889

[30] Foreign Application Priority Data June 7, 1972 Japan 47056103 [52] US. Cl 61/72.4; 61/726 [51] Int. Cl. E02F 5/02; F16L 1/00 [58] Field of Search 61/724, 72.5, 72.6, 72.7,

[56] References Cited UNITED STATES PATENTS 2,722,181 11/1955 Hash 61/72.6

3,333,432 8/1967 Hale et a1, 61/724 3,434,297 3/1969 Gretter et al. 61/724 3,641,780 2/1972 Ede 61/724 3,722,224 3/1973 Roy t t 6l/72.4 3,824,798 7/1974 Shiroyama 61/724 Primary Examiner.1acob Shapiro Attorney, Agent, or F irmArmstrong, Nakaido 8L Wegner [5 7] ABSTRACT A ditching machine for digging a ditch for submarine cable comprising a main body having stabilizing means which is divided into front and rear parts and jointed so as to be bendable only up and down, and a cutting bit mounted rigidly under said rear part of the main body, to prevent the entering of the head of said stabilizing means into earth and sand on the sea-bottom and to provide stable cable burying without regard to whether the layer at sea-bottom is hard or soft.

4 Claims, 3 Drawing Figures DITCHING MACHINES FOR SUBMARINE CABLE The present invention relates to a ditching machine for digging a ditch for a submarine cable on the seabottom.

A prior ditching machine for a submarine cable comprises a cutting bit underneath the main body thereof to dig a ditch of desired width in the sea-bottom, and a stabilizing wing, which is a ski-shaped sledge or a stabilizing plate to stabilize the bit and the main body.

Said bit and stabilizing means are two important elements of a ditching machine. In prior art, said stabilizing means is mounted on a frame together with said bit and integrated with it. And when the cutting edge of a bit reaches the desired depth in the sea-bottom, said stabilizing means comes into contact with the seabottom.

However, the nature of the strata at sea-bottom is, generally, not uniform along the entire length of a submarine cable route. Consequently, if a ditching machine meets a hard stratum, the cutting edge of the bit of the ditching machine may not be able to reach the desired depth because of the difficulty in sufficiently penetrating the sea-bottom at that point. Generally, the bit of a ditching machine is mounted on acentral or rear part of a ditching machine for mechanical reasons. In this case if the ditching machine meets a hard stratum, the rear part of the ditching machine is pushed up, and the lower surface of the stabilizing plate, which is rigidly mounted on the ditching machine, is not able to contact the surface of the sea-bottom. Further the front part of the stabilizing means is sometimes thrusts into earth and sand of the top layer or stratum of the seabottom.

In order to avoid said disadvantage, one prior stabilizing means has its front portion bent upward at an angle while another prior stabilizing means has its front portion curved upward similar to a ski. However, in the former the bent portion is able to plane-contact, the surface of the sea-bottom at only one angle of the stabilizing means, while in the latter only a very small area of the curved portion may come into linear-contact with the surface of the sea-bottom at any angle of the ditching machine. In addition, with the latter, said curved portion of the stabilizing means provides insufficient stabilizing effect to a ditching machine while exerting an extravagantly large pulling force against the ditching machine. One prior technique to avoid said disadvantage is to use a short cable between the ditching machine and a cable ship, to lift up the front part of the stabilizing means. On the other hand, said prior techniques sometimes reduces the ditching ability of the ditching machine by reducing its weight, and in the worst case both right and left stabilizing means leave the surface of the sea-bottom. Naturally when the stabilizing means is no longer on the surface of the sea bottom its capability of stabilizing against the rolling of the ditching machine is completely lost.

Though the prior stabilizing means for ditching machines are capable of preventing the excessive sinking of the ditching machine due to its own weight when the surface of the sea bottom is soft, such effect is not essential and can be easily obtained only by providing some area for plane-contact at the rear part of a bit.

As is apparent from the above discussion, the essential disadvantage of prior ditching machines is that although prior ditching machines are well stabilized against rolling under the burying operation in the soft stratum such ditching machines are not stabilized against rolling at the time a cutting bit is digging out the trench in the hard stratum of the sea-bottom where stabilization is most required.

A further disadvantage of prior ditching machines is that stabilization of ditching machines against thrusting the front part of the ditching machines into earth and sand has not been solved yet.

The object of the present invention is to provide a ditching machine which overcomes the abovementioned disadvantages.

A further object of the present invention is to provide a ditching machine which is always stable under the conditions whether the depth of a trench being dug is deep or shallow due to the nature of surface of the sea bottom.

In order to accomplish said objects, a ditching machine according to the present invention comprises a main body composed of a main frame and having stabilizing means on both sides of the same, a cutting bit mounted rigidly under said main body, wherein said stabilizing means is divided into front and rear parts, which are jointed so as to be bendable only up and down.

Further features and advantages of the present inven' tion will be apparent from the ensuing description with reference to the accompanying drawings to which, however, the scope of the invention is in no way limited.

FIG. 1(A) is a plane view of a ditching machine having stabilizing means according to the present invention;

FIG. 1(B) is a side view of a ditching machine having stabilizing means according to the present invention;

FIG. 2 is a fragmentary side view of a ditching machine having stabilizing means according to the present invention.

In FIG. 1(A) and FIG. 1(B), a main body of a ditching machine of the present invention is divided into two parts. In this example, a ditching machine comprises a pair of main bodies 1 (1a, lb) positioned one behind the other at the center of the ditching machine, a pair of cutting bits 2 (2a, 2b) at the rear part of the ditching machine below the main body 1, and a pair of identical sliding stabilizing sledges 3 (3a, 3b) positioned symmetrical to the main body 1.

Said main body 1 and said stabilizing sledge 3 are divided into two parts in order to stabilize the ditching machine. The main body 1 comprising a cable path 7 is divided into a front body 1a and a rear body lb in front of the upper portion of the cutting bit 2 as shown in FIG. 1(A) and FIG. 1(B). A working boat (not shown) tows a ditching machine with pull wire 4, and submarine cable 6 is supplied to the ditching machine through a cable guiding means 5 from the cable ship. Said submarine cable 6 is laid in a ditch dug on sea bottom 8 by said cutting bit 2. Each divided bodies 1a and lb is supported by a pair of stabilizing sledges 3 for stabilizing the attitude of the ditching machine. Said stabilizing sledges 3 are positioned symmetrical to the main body I. Said sledges 3 are also divided into two parts 3a and 3b at the same point that the main body is divided. Each pair of divided sledges are rigidly connected to the related divided main body by supporting beams 10a and 10b extending laterally from the main divided bodies Ia and lb, respectively. Further the front and rear parts of the pair of divided sledges are bendably connected to each other by a pair of joints 1 l. The jointed main bodies 1 (la, lb) can bend only up and down and cannot bend right and left.

Many modifications of the embodiment described above are possible.

For instance, the front and rear parts of the divided main bodies 1 (la, 1b) may be jointed so as to be bendable up and down instead of jointing the front and rear parts of the divided sledges 3 (3a, 3b). Further, a single sledge is possible instead of a pair of sledges.

In said embodiment, a cutting bit 2 comprises two parts and 2b, the width of front cutting bit 2a is larger than that of rear cutting bit 2b. At the rear outlet of the cable path 7 a cable press means comprising a press block 12 pivotably connected to said cable path 7 of said main body 1 by a pin 13 is provided. Said cable press means makes it possible to lay both thick repeaters and thin submarine cables at the bottom of a dug out ditch. However, any construction at the rear part of the present ditching machine including a cutting bit is possible within the spirit of the present invention. Further, a ditching machine divided into more than three parts which are jointed bendably is possible according to the same principle as the present invention.

According to the construction mentioned above, as the attitude of the ditching machine of the present invention is always stabilized, cable ship can carry out long continuous operation of burying submarine cable. Even if the ditching machine meets a hard stratum of the sea bottom and the rear part of the ditching ma chine equipped with the cutting bit floats upward as shown in FIG. 2, the head of the front sledges do not thrust into earth and sand. Further the front part of the ditching machine does not float upward, provided some weight is applied at the front part of the ditching machine.

As mentioned above, it should be understood that a ditching machine according to the present invention is very useful and extremely effective.

It should be understood of course that the embodiment disclosed is merely illustrative and is not intended to limit the scope of the invention.

What we claim is:

l. A ditching machine comprising a main body having front and rear portions, a cutting bit mounted on said rear portion, stabilizing means mounted on the sides of the front and rear portions of said main body, and pivotal joint means having a horizontal axis for joining the rear of the front portion and the front of the rear portion of said main body, such that said rear portion moves with respect to said front portion only about the horizontal axis of the pivotal joint means.

2. A ditching machine according to claim 1, further comprising a press block pivotably connected to the outlet of a cable path of said rear part of said main body.

3. A ditching machine according to claim 1, wherein said stabilizing means are a pair of sledges.

4. The ditching machine of claim 1 wherein said joint means are coupled to said stabilizing means. 

1. A ditching machine comprising a main body having front and rear portions, a cutting bit mounted on said rear portion, stabilizing means mounted on the sides of the front and rear portions of said main body, and pivotal joint means having a horizontal axis for joining the rear of the front portion and the front of the rear portion of said main body, such that said rear portion moves with respect to said front portion only about the horizontal axis of the pivotal joint means.
 2. A ditching machine according to claim 1, further comprising a press block pivotably connected to the outlet of a cable path of said rear part of said main body.
 3. A ditching machine according to claim 1, wherein said stabilizing means are a pair of sledges.
 4. The ditching machine of claim 1 wherein said joint means are coupled to said stabilizing means. 